*{
    box-sizing: border-box;
}
body{
    background-color: #e1e1e1;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    text-align: center;
    overflow: hidden;

    margin: 0;
}
.key{
    border: 1px solid #999;
    border-color: #eee;
    box-shadow: 1px 1px 3px rgba(0,0,0,.1);
    display: inline-block;
    align-items: center;
    font-size: 20px;
    font-weight: bold;
    padding: 20px;
    flex-direction: column;
    margin: 10px;
    /* 宽度可以稍微地适配 */
    min-width: 150px;
    position: relative;
}
/* 上面的小字 */
.key small{
    position: absolute;
    top: -24px;
    left: 0;
    text-align: center;
    width: 100%;
    color: #555;
    font-size: 14px;
}
@media(max-width:768px){
    .key{
        margin: 10px 0;
    }
}